The present invention relates to the field of marine vessels and, more particularly, to an apparatus and method for detecting an object interrupting a perimeter about a vessel at rest on the water. The invention is applicable to any watercraft, including pleasure craft, as well as merchant and military vessels.
Recent events have made it increasingly evident that docked military ships and other vessels are vulnerable to the threat presented by the approach of one or more small boats and/or ground vehicles from dockside. These threats increase significantly when a ship is at anchor or docked in a foreign port where port security standards may be low and subject to penetration by adversary forces.
The harbor environment is generally very complicated, as typically there is much activity and many ships and smaller boats are in close proximity. Several security guards posted around the ship would be required to provide complete coverage. However, humans are subject to fatigue brought on by long hours of watch duty. In addition, night coverage presents obvious problems for the security guard, as constant illumination of the vessel and it surroundings is generally not practical.
In the realm of pleasure craft such as yachts and the like, it is well known that occassionally a vessel moored, anchored, or docked may be approached and boarded by modern day pirates. The apparatus and method herein described are equally applicable for providing a level of added vessel security for these pleasure craft and their crews and passengers. In addition, for example, with leasure passenger cruise ships, the presentely described invention could be employed as a warning system to indicate that a passenger launch is approaching the ship, and an alarm triggered thereby would alert the crew to be prepared to receive the launch and its passengers. Additional applications of the invention will, no doubt, occur to those skilled in the art.
Accordingly, there is a need for an automated system capable of maintaining constant observation of the vessel perimeter. Such a sensor system should be inconspicuous, reliable, and versatile enough to accommodate the varying target signatures in the harbor environment. In addition, the apparatus should be sufficiently sturdy to survive the adverse conditions of the marine environment, which over time will be encountered even in sheltered harbors.
With the foregoing in mind, the present invention advantageously provides for a ship at rest on a water surface, an apparatus for detecting an object approaching the ship along an approach surface, which could be the surface of the water, or the surface of a dock, for example. The apparatus includes a laser light curtain, a pulsed laser rangefinder to generate the laser light curtain, a power source, a processor to obtain and process data from the rangefinder, and at least one display to display information obtained from the processed data.
The laser light curtain comprises at least one pulsed laser light beam extending radially from the ship toward a perimeter thereabout, the laser light curtain being positioned spaced apart from and approximately parallel to the approach surface for detecting an object interrupting the light curtain. At least one pulsed laser rangefinder is connected to the ship and positioned outboard therefrom to generate the laser light curtain. A power source is connected to the pulsed laser rangefinder to supply power thereto. A processor is connected to the pulsed laser rangefinder to process data therefrom, and at least one display connected to the processor to display information obtained from the processed data.
The invention includes a method embodied in the disclosed apparatus. The method includes deploying at least one pulsed laser rangefinder adjacent the ship and outboard therefrom so as to be a predetermined distance spaced apart from the approach surface, be that the surface of the water or the surface of a dock or pier. The rangefinder operates by generating a pulsed laser beam from the pulsed laser rangefinder, and reflecting the generated pulsed laser beam from a rotating mirror in the pulsed laser rangefinder so as to form a laser light curtain spaced apart from the approach surface and extending away from the ship along at least a partial radial perimeter about the pulsed laser rangefinder. The method then includes detecting a pulsed laser beam reflected back to the pulsed laser rangefinder from an object interrupting the laser light curtain, and calculating the direction of movement and speed of the interrupting object relative to the ship by processing data associated with the pulsed laser beam reflected back from the interrupting object.